1. Technical Field
The present invention generally relates to aircraft equipped with an image sensor and, more particularly, to a method and apparatus for navigating the aircraft from an image of the runway.
2. Background Information
Aircraft, such as airplanes, helicopters, and spacecraft, are an increasingly important mode of transportation. Safely landing the aircraft is a critical aspect of operating the aircraft. Safely landing the aircraft requires accurately navigating the aircraft during runway approaches. Accurately navigating the aircraft includes directing the aircraft toward the runway and avoiding obstacles on or near the runway. This requires one of two things: (1) the pilot has a clear view of the runway and the obstacles on the runway from the time that the aircraft is a predetermined height above the earth until the time that the aircraft lands, or (2) the aircraft is provided with accurate navigational information. In low visibility conditions such as darkness, fog, low cloud cover, and other low visibility weather conditions, the pilot may not have a clear view of the runway and the obstacles on the runway when the aircraft is below the predetermined height (referred to as a low approach). In those situations, accurate navigational information is required to safely land the aircraft.
The navigational information traditionally used in an aircraft consists of Navigational Data (Nav Data). Nav Data is generated by many sources such as sensors on the aircraft, satellites, ground-based devices, and the aircraft database. Examples of sensors on the aircraft include an inertial reference system (IRS), and an attitude/heading reference system (AHRS). Examples of ground-based devices include an instrument landing system (ILS), a microwave landing system (MLS), and a differential global positioning system (DGPS). Examples of Nav Data include pitch, roll, yaw, Nav Data lateral deviation, Nav Data vertical deviation, barometric altitude, global positioning information, and runway data such as runway heading, runway position, runway length, and runway width.
Nav Data cannot be used to navigate the aircraft to avoid obstacles on or near the runway because Nav Data does not provide information about these obstacles. In addition, even in the absence of obstacles, many sources of Nav Data are not accurate enough to safely land the aircraft while making a low approach. The sources of Nav Data that have the required accuracy to safely make low approaches in the absence of obstacles are some ground-based devices. These instruments either provide Nav Data for an entire airport (for example, DGPS), or provide Nav Data for an individual runway (for example ILS). These devices are expensive, with the expense increasing as the device maintains acceptable accuracy at lower predetermined heights. As a result, many airports are not equipped with these devices, or only a small number of the runways at these airports are equipped with these devices.
Thus, there is a need to provide additional navigational information to an aircraft that indicates obstacles on or near the runway, is accurate enough to safely land the aircraft, and is generated by a relatively inexpensive device.